The invention concerns lubricating compositions having improved properties. Another aspect of the invention relates to additive compositions which impart antiwear and antiscuffing properties to lubricating compositions used for internal combustion engines such as gasoline engine and diesel engine.
Additives known as antiwear agents are employed to increase the load carrying capacity of lubricants. The antiwear agents promote the formation of a surface film and thereby prevent wear of the contacting surfaces. The mechanical efficiency enhanced by decreased friction loss further results in decreased fuel consumption and energy savings.
It is known that certain organic molybdenum complexes possess antiwear properties as well as other desirable lubricating characteristics as disclosed in U.S. Pat. No. 4,889,647. Organic molybdenum complexes can be combined with sulfur donors as described in U.S. Pat. No. 4,164,473. Surprisingly, it has been now discovered that the molybdenum complexes described therein produce a synergistic antiwear effect in combination with certain organic sulfur compounds. Unexpectedly, the synergistic composition lowers the friction characteristics of the protected surface by effecting changes in its metallurgy.
According to the invention, there are provided synergistic antiwear compositions consisting essentially of:
(1) an organomolybdenum complex prepared by reacting about 1 mole fatty oil, about 1.0 to 2.5 moles diethanolamine and a molybdenum source sufficient to yield about 0.1 to 12.0 percent of molybdenum based on the weight of the complex, and
(2) an organic sulfur compound selected from the group consisting of
(i) 1,3,4-thiadiazole compounds of the formula: 
wherein R and R1 are independently selected from C1-22-alkyl groups, terpene residue and maleic acid residue of the formula 
and R2 and R3 represent C1-22-alkyl and C5-7-cycloalkyl groups, R or R1 and either R2 or R3 may be hydrogen;
(ii) bisdithiocarbamate compounds of the formula 
wherein R4, R5, R6, and R7 are aliphatic hydrocarbyl groups having 1 to 13 carbon atoms and R8 is an alkylene group having 1 to 8 carbon atoms;
(iii) dithiocarbamates of the formula 
wherein R4 and R5 represent alkyl groups having 1 to 8 carbon atoms, M represents metals of the periodic groups IIA, IIIA, VA, VIA, IB, IIB, VIB, VIII and a salt moiety formed from an amine of the formula 
xe2x80x83and R13 being independently selected from hydrogen and aliphatic groups having 1 to 18 carbon atoms and n is the valence of M;
(iv) phosphorodithioates of the formula 
wherein X and X1 are independently selected from S and O, R9 and R10 represent hydrogen and alkyl groups having 1 to 22 carbon atoms, M represents metals of the periodic groups IIA, IIIA, VA, VIA, IB, IIB, VIB, VIII and a salt moiety formed from an amine of the formula 
xe2x80x83R11, R12 and R13 being independently selected from hydrogen and aliphatic groups having 1 to 18 carbon atoms and n is the valence of M; and
(v) phosphorodithioate esters of the formula 
wherein R4and R5 may be the same or different and are selected from alkyl groups having 1 to 8 carbon atoms; and the ratio of the molybdenum complex to the sulfur compound is about 1:5 to about 5:1.
Another aspect of the invention concerns lubricating compositions having improved lubricating properties and comprising a major portion of an oil of lubricating viscosity and about 0.1 to 10.0 percent by weight of a composition comprising (1) an organomolybdenum complex prepared by reacting about 1 mole fatty oil, about 1.0 to 2.5 moles diethanolamine and a molybdenum source sufficient to yield about 0.1 to 12.0 percent of molybdenum based on the weight of the complex and (2) a sulfur compound of the formula I, II, III, IV or V.
The organomolybdenum component of the invention is prepared by sequentially reacting fatty oil, diethanolamine and a molybdenum source by the condensation method described in U.S. Pat. No. 4,889,647, incorporated herein by reference. The reaction yields a reaction product mixture. The major components are believed to have the structural formulae 
wherein R represents a fatty oil residue. The preferred fatty oils are glyceryl esters of higher fatty acids containing at least 12 carbon atoms and may contain 22 carbon atoms and higher. Such esters are commonly known as vegetable and animal oils. Vegetable oils particularly useful are oils derived from coconut, corn, cottonseed, linseed, peanut, soybean and sunflower seed. Similarly, animal fatty oils such as tallow may be used.
The source of molybdenum is an oxygen-containing molybdenum compound capable of reacting with the intermediate reaction product of fatty oil and diethanolamine to form an ester-type molybdenum complex. The source of molybdenum includes, among others, ammonium molybdates, molybdenum oxides and mixtures thereof.
The 1,3,4-thiadiazoles of formula I may be prepared by the method disclosed in U.S. Pat. No. 4,761,842 and U.S. Pat. No. 4,880,437 incorporated herein by reference. Terpene residues are preferably derived from pinene and limonene having the structural formulae given hereinbelow. 
The alkyl groups represented by R and R1 contain preferably 1 to 22 carbon atoms and may be branched or straight chain. Particularly preferred are compounds wherein both alkyl groups together contain a total of at least 22 carbon atoms. Groups R2 and R3 in the formula I represent branched or straight chain alkyl groups containing 1 to 22 carbon atoms and cyclic aliphatic groups such as cyclohexyl, cyclopentyl and cycloheptyl.
The bisdithiocarbamates of formula II are known compounds described in U.S. Pat. No. 4,648,985, incorporated herein by reference. The compounds are characterized by groups R4 to R7 which are the same or different and are hydrocarbyl groups having 1 to 13 carbon atoms. Preferred are branched or straight chain alkyl groups having 1 to 8 carbon atoms. The group R8 is an aliphatic group such as straight and branched alkylene groups containing 1 to 8 carbons. Particularly preferred is methylenebis (dibutyldithiocarbamate) available commercially under the tradename VANLUBE(copyright) 7723 from R.T. Vanderbilt Company, Inc.
The dithiocarbamates of the formula III are known compounds. One of the processes of preparation is disclosed in U.S. Pat. No. 2,492,314. Groups R4 and R5 in the formula III represent branched and straight chain alkyl groups having 1 to 8 carbon atoms. Particularly preferred are antimony and zinc dithiocarbamates.
The phosphorodithioates of the formula IV are known, commercially available materials. One of the processes of preparation is taught by U.S. Pat. No. 4,215,067. Groups R9 and R10 represent branched and straight chain alkyl groups having 1-22 groups and may be derived from fatty acids. Particularly preferred are zinc phosphorodithioates. The metal ion in formula III and IV may be selected from the following groups of the Periodic Table: IIA, IIIA, VA, VIA, IB, IIB, VIB and VIII. Amine salts of the compounds are also useful synergists of the invention. Exemplary, salts include, among others, those prepared from alkyl amines and mixed alkyl amines. Particularly useful are fatty acid amines.
The phosphorodithioate esters of the formula V are known compounds. One of the processes of manufacture is disclosed in U.S. Pat. No. 3,567,638. Groups R4 and R5 in the formula V may be the same or different and may be selected from branched and straight chain alkyl groups. Preferred are groups containing 1 to 8 carbon atoms.
The sulfur compounds are known to possess certain lubricating properties such as oxidation, wear and corrosion inhibition in various lubricating media. Sometimes, however, the sulfur compounds alone do not provide adequate antiwear protection for the varied heavy duty applications of many industrial and automotive lubricants.
Moreover, under certain conditions, the high concentrations of sulfur compounds may produce an adverse effect on the overall performance of the lubricant. For instance, the so called sulfur donors may produce undesirably large amounts of sulfur compounds on the protected surface.
Unexpectedly, the above sulfur compounds produce synergistic antiwear effect when combined with organomolybdenum compounds in certain ratios. The synergistic compositions of the invention appear to produce metallurgical changes in the surface to be protected. The change manifests in lower friction and consequently, higher antiwear protection. Synergism is displayed by compositions containing about 1 to 5 parts by weight of the sulfur compound to about 5 to 1 part by weight of the molybdenum compound and preferably about 1 to 2 parts by weight of the sulfur compound to about to 2 to 1 parts by weight of the molybdenum compound.
Another advantage of the synergistic combination is that the compositions possess good antioxidant properties. Even in instances where the sulfur compounds do not possess an antioxidant activity, the combination with the molybdenum complexes provides a composition with good overall antioxidant properties.
The synergistic compositions may be incorporated in any lubricating media by known methods. The compositions impart antiwear as well as oxidation inhibiting and extreme pressure properties to natural and synthetic lubricants formulated as oils or greases.
The base oils employed as lubricant vehicles are typical natural and synthetic oils used in automotive and industrial applications such as, among others, turbine oils, hydraulic oils, gear oils, crankcase oils and diesel oils. Natural base oils include mineral oils, petroleum oils, paraffinic oils and the ecologically desirable vegetable oils. Typical synthetic oils include ester-type oils such as silicate esters and pentaerythritol esters, hydrogenated mineral oils, silicones and silanes.
The compositions of the invention may be incorporated in the lubricant in an amount effective to produce the desired antiwear characteristics. An amount from about 0.1 to 10.0 percent will be sufficient for most applications. A preferred range is from about 0.5 to about 3. 0 percent by weight of the total lubricant composition.
The lubricating compositions may contain other conventional additives depending on the intended use of the lubricant. For example, formulations may contain rust inhibitors such as metal salts of alkylnaphthalenesulfonic acids. Other additives are antioxidants such as alkylated diphenylamines, e.g. commercially available products VANLUBE(copyright)SL, DND, NA, 81 and 961 manufactured by R.T. Vanderbilt Company, Inc., Naugalube(copyright) 640, 680 and 438L manufactured by Uniroyal Chemical and Irganox(copyright)L-57 manufactured by Ciba-Geigy. Other additives include, among others, demulsifiers, dispersants, detergents and supplemental antioxidants.
The grease formulations may contain various thickening agents such as, among others, silicate minerals, metal soaps and organic polymers.